Electromagnetic vibrating diaphragm pump

ABSTRACT

An electromagnetic vibrating diaphragm pump capable of preventing fluid such as air from leaking to an oscillator side. This diaphragm is sandwiched by an inner center plate and an outer center plate and is fixed by inserting the mounting screw parts of the oscillator into a through hole provided at the center of the outer and inner center plates. A cylindrical projecting portion is formed at the center of the inner center plate on its oscillator side, and this projecting portion is fitted into the concave groove formed at the ends of the supporting member of the oscillator so as to be sealed in an airtight manner with a ring-shaped elastic member inbetween.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No. PCT/JP2012/059647 International Filing date, 9 Apr. 2012, which designated the United States of America, and which International Application was published under PCT Article 21 (s) as WO Publication 2012/141125 A1 and which claims priority from, and the benefit of, Japanese Application No. 2011-091237 filed 15 Apr. 2011, the disclosures of which are incorporated herein by reference in their entireties.

BACKGROUND

The presently disclosed embodiment relates to an electromagnetic vibrating diaphragm pump utilized for aeration of septic tanks for home use, oxygen supply for fish culturing tanks, exhalation for whirlpool baths, and other applied equipment, etc. More specifically, it relates to an electromagnetic vibrating diaphragm pump structured to prevent fluid from passing through the fixing part between the end of an oscillator and a diaphragm and leaking into the pump from outside.

An electromagnetic vibrating diaphragm pump is structured to comprise diaphragms made of rubber, for example, fixed to both ends of an oscillator having magnets fixed thereto, and electromagnets are provided in a manner to face the magnets on the oscillator. The oscillator and the electromagnets are surrounded by a housing and pump casings covers the outer diaphragms. Additionally, the oscillator oscillates in accordance with the polarity change of the electromagnets changing in accordance with the change in the phase of an AC source applied to the electromagnets such that the diaphragms vibrate so as to repeatedly suction and discharge fluid such as air.

The oscillator and the diaphragm are fixed in a structure shown in FIG. 7, for example. Namely, in FIG. 7, 103 represents the oscillator and mounting screw parts 103 c are firmly attached at both ends of a supporting member 103 b having a permanent magnet 103 a fixed thereto. While the diaphragm 104 made of rubber member, etc. has a through hole at its center, and is sandwiched between a center plate 107 b on its electromagnet side (hereinafter referred to as inner, simply) where a projection fitting into this through hole is formed and a center plate 107 a on its pump casing side, opposite to the electromagnet side, (hereinafter referred to as outer, simply). The mounting screw part 103 c of the above-mentioned oscillator 103 is inserted into the through hole 110 provided at the center of these inner and outer center plates 107 b, 107 a, and fastened by a nut 106 from outside with a washer 105 inbetween, to do the fixing work (see Patent Document 1, for example). These outer and inner center plates 107 a, 107 b are made of metal plates or plastic, and fixed tightly to the oscillator 103 to withstand vibration. Here, the pump casing, although not illustrated, is provided to the outer side of this diaphragm 104. The pump casing comprises a compression chamber adjacent to the diaphragm, a suction chamber provided adjacent to the compression chamber interposed by a suction valve and an exhaust chamber provided adjacent to the compression chamber interposed by an exhaust valve.

Additional background information may be found in Japanese publication JP 2003-035266 A.

SUMMARY

The structure where the mounting screw part 103 c of the oscillator 103 is inserted into the through hole 110 of the above described outer and inner center plates 107 a, 107 b so as to be fixed with the nut 106 is preferred in terms of very easy assembly. However, in some cases, a gap may be formed between the mounting screw part 103 c and the through hole 110 of the outer and inner center plates 107 a, 107 b. Additionally, depending on how tightly the nut 106 is fastened, a gap may be formed between the end of the supporting member 103 b and the inner center plate 107 b, too. Therefore, there is an issue that fluid such as air suctioned into the compression chamber leaks to the oscillator 103 side where the electromagnet, etc. is arranged, as indicated by arrows a1, a2 in FIG. 7.

When such liquid leakage causes the amount of fluid discharged from the compression chamber to decrease to less than the amount of fluid suctioned into the compression chamber, the utilization ratio of fluid such as air suctioned into the compression chamber decreases, which is not preferred because it reduces pump efficiency. Moreover, in some cases, dangerous gas such as hydrogen for a hydrogen circulation pump, etc. may be discharged with a pump. It is dangerous to allow such gas to leak to the electromagnet side. Furthermore, because in some cases liquid may be suctioned or discharged, there is a problem that liquid flowing to the electromagnet side causes a short circuit in an electric system such as an electromagnet coil and so on.

On the other hand, as a method for preventing such liquid leakage, for example, it is possible to seal with a gasket between the washer 105 and the outer center plate 107 a. However, if the oscillator 103 is fixed with a gasket inbetween, it becomes difficult to securely seal between the mounting screw part 103 c and the through hole 110 of the outer and inner center plates 107 a, 107 b depending on how tightly the nut 106 is fastened. Moreover, if a gasket is provided between the washer 105 and the outer center plate 107 a, the oscillator 103 can be tilted depending on how tightly the nut 106 is fastened, and the tilt, if any, allows the gap between the oscillator 103 and the electromagnet to vary easily, which leads to an issue of difficulty in stabilizing diaphragm pump performance among products.

Moreover, the issue of fluid leakage of the electromagnetic vibrating pump is not limited only to between the oscillator 103 and the outer and inner center plates 107 a, 107 b. For example, a conventional electromagnetic vibrating diaphragm pump had a diaphragm support 108 and a partition wall 109 a constituting a compression chamber (not illustrated) of a pump casing 109 sandwiching the outer periphery end 104 a of a diaphragm 104 as shown in FIG. 8, the outer periphery end 104 a of the diaphragm 104 and the partition wall 109 a of the compression chamber (not illustrated) of the pump casing 109 assembled by just being placed on each other. Therefore, fluid suctioned into the compression chamber (not illustrated) of a pump leaks out of the pump casing 109 through the gap between a flange 104 a of the diaphragm 104 and the partition wall 109 a of the pump casing 109, following the order indicated by arrows b1-b3, and thus the amount of the fluid discharged from the compression chamber decreased to less than the amount of fluid suctioned into the compression chamber, to raise an issue of decreasing pump performance.

The presently disclosed embodiment was made in the light of the above conditions, and the object of the presently disclosed embodiment is to provide an electromagnetic vibrating diaphragm pump which improves pump efficiency by preventing fluid such as air from leaking out to the oscillator side while stabilizing pump performance among products by maintaining a gap between the oscillator and the electromagnet constantly among products, and does not cause damage to components or harm to human bodies, etc. even when suctioning and discharging liquid or dangerous gas such as hydrogen.

Moreover, another object of the presently disclosed embodiment is to improve the pump efficiency by preventing the leakage of air, etc. from the abutment surface of the pump casing and the diaphragm.

The electromagnetic vibrating diaphragm pump of the presently disclosed embodiment comprises an oscillator having two magnets on at least one surface side of a plate-like supporting member made of non-magnetic material and having mounting screw parts fixed to both ends of a central axis of the supporting member, disc-shaped diaphragms fixed to the mounting screw parts at both ends of the supporting member, an electromagnet provided to face the magnets and pump casings fixed to respective outer peripheries of the diaphragms provided at both ends and individually covering the outer side of the diaphragms, wherein the diaphragm is sandwiched by an inner center plate provided on the magnet side of the diaphragm and an outer center plate provided on the side opposite to the magnet side of the diaphragm, the end of the oscillator is inserted into and fixed to a through hole provided at the center of the inner and outer center plates, a cylindrical projecting portion is formed at the center of the inner center plate on the oscillator side, and a concave groove capable of fitting the projecting portion is formed at the end of the supporting member of the oscillator such that the projecting portion and the concave groove are sealed in an airtight manner with a ring-shaped elastic member inbetween.

It is preferred that a protruding portion holding the side surfaces of both ends of the supporting member constituting the oscillator is formed on the surface of the inner center plate on its oscillator side so as to position the supporting member. The side surface herein includes, in addition to the side surface in the thickness direction of the plate-like supporting member, the side at the end of the planar part of the plate-like supporting member.

It is preferred that the pump casing has a compression chamber adjacent to the diaphragm, an exhaust chamber connected to the compression chamber via an exhaust valve and a suction chamber connected to the compression chamber via a suction valve, and a rib digging into the diaphragm is formed on a joint surface jointing the diaphragm on the partition wall of the compression chamber.

The electromagnetic vibrating diaphragm pump of the presently disclosed embodiment is structured such that a cylindrical projecting portion is provided at the center of an inner center plate on its oscillator side and a concave groove capable of fitting the projecting portion is formed at the end of a supporting member of the oscillator, the projecting portion and the concave groove being sealed in an airtight manner with a ring-shaped elastic member inbetween. Therefore, with the groove formed beforehand on an outer periphery of a site where a mounting screw part is fixed at both ends of the supporting member of the oscillator and with an O-ring and the like inserted in this groove, by only press-fitting the mounting screw part into a through hole of the inner center plate, assembly work can be done and also airtight sealing can be ensured. Furthermore, because this sealing is a closely attached sealing in radial direction, of the concave groove formed on the supporting member of the oscillator, the ring-shaped elastic member fitting into the concave groove and the cylindrical projecting portion, the dimension among components such as a gap between the oscillator and the electromagnet is not affected, regardless of the strength of the elasticity. Therefore, it is possible to stabilize pump performance among products. In addition, even when an unexpected external force is applied to the oscillator, for example during assembling stage, it has an effect of preventing damage to the diaphragm because of its absorptive capacity for such a large external force. By providing such ring-shaped elastic member, the amount of fluid discharged from the compression chamber is not less than the amount of fluid suctioned into the compression chamber, and as a result, the decrease of pump performance can be prevented. Furthermore, if the fluid is liquid, it is possible to prevent pump failure due to short-circuited electromagnet coils, etc. when fluid penetrates to the oscillator side from taking place.

Furthermore, on the surface of the inner center plate on its oscillator side, a protruding portion for holding the side surfaces of both ends of the supporting member is formed such that the oscillator is prevented from rotating with respect to the inner center plate and the positioning of the supporting member can be performed easily, allowing stable operation of the pump. In addition, because the protruding portion of the inner center plate can be served as a guide when inserting the mounting screw part of the oscillator into the through hole formed on the center plates, the supporting member of the oscillator and the inner center plate are assembled easily.

Furthermore, by forming a rib digging into the diaphragm on the joint surface jointing the diaphragm on the partition wall of the compression chamber of the pump casing, situations are avoided where liquid suctioned into the compression chamber leaks out from the gap produced at the joint between the diaphragm and the pump casing and the amount of fluid discharged from the compression chamber is less than the amount of fluid suctioned into the compression chamber. As a result, it is possible to prevent decreasing of pump performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A sectional explanatory view of one embodiment of the electromagnetic vibrating diaphragm pump of the presently disclosed embodiment.

FIG. 2 A schematic explanatory view of the electromagnet and oscillator part of the electromagnetic vibrating diaphragm pump shown in FIG. 1.

FIG. 3 A sectional explanatory view showing the mounting part between the diaphragm and the oscillator of FIG. 1.

FIG. 4 A side view of the end of the oscillator on the inner center plate side.

FIG. 5 A front view of the inner center plate as seen from the oscillator side.

FIG. 6 An enlarged view of a portion A of FIG. 1.

FIG. 7 A sectional explanatory view showing a conventional example of a mounting part of an oscillator and a diaphragm.

FIG. 8 A sectional explanatory view showing a conventional example of a joint portion between a conventional diaphragm and partition wall of a compression chamber.

DETAILED DESCRIPTION

The embodiments of the presently disclosed embodiment will be described below with reference to FIGS. 1-6.

FIG. 1 shows a sectional explanatory view of an electromagnetic vibrating diaphragm pump according to the first embodiment of the presently disclosed embodiment, and FIG. 2 shows a schematic explanatory view of an electromagnet and oscillator part of the electromagnetic vibrating diaphragm pump shown in FIG. 1. As shown in FIG. 1, this electromagnetic vibrating diaphragm pump 1 (hereinafter abbreviated as pump) comprises an oscillator 2 having two magnets (permanent magnets) 2 b 1, 2 b 2 provided on a plate-like supporting member 2 a made of nonmagnetic material and having mounting screw parts 2 c fixed at both ends of a central axis of the supporting member 2 a, disc-shaped diaphragms 3 fixed to the mounting screw parts 2 c at both ends of the supporting member 2 a of the oscillator 2, electromagnets 4 a, 4 b provided to face the magnets 2 b 1, 2 b 2, and pump casings 5 fixed to outer peripheries of the respective diaphragms 3 and covering the outer side of the respective diaphragms 3. The mounting screw part 2 c is closely attached and fixed, for example by being integrally molded onto the supporting member 2 a made of resin during the formation of the supporting member 2 a by resin molding, etc.

The diaphragm 3 is sandwiched by an inner center plate 6 b provided on its magnet 2 b 1, 2 b 2 side of the diaphragm 3 and an outer center plate 6 a provided on the side opposite to the magnet 2 b 1, 2 b 2 side of the diaphragm 3, and the mounting screw parts 2 c fixed to the oscillator 2 are inserted into the through hole 6 c provided at the center of the outer and inner center plates 6 a, 6 b and then fastened from outside through a washer 8 by a nut 9, such that the supporting member 2 a of the oscillator 2 and the diaphragm 3 are fixed to each other.

As shown in FIG. 3, a cylindrical projecting portion 6 b 1 is formed at the center of the inner center plate 6 b on its oscillator 2 side, a concave groove 2 d capable of fitting the projecting portion 6 b 1 of the inner center plate 6 b is formed at the end of the supporting member 2 a of the oscillator 2, and the projecting portion 6 b 1 of the inner center plate 6 b and the concave groove 2 d of the supporting member 2 a of the oscillator 2 are sealed in an airtight manner with an O-ring 7 inbetween as a ring-shaped elastic member.

As shown in FIG. 2, the electromagnets 4 a, 4 b comprise E-shaped electromagnet cores 4 a 1, 4 b 1 and electromagnet coils 4 a 2, 4 b 2 wound around the electromagnet cores 4 a 1, 4 b 1. As shown in FIG. 1 and FIG. 2, two magnets 2 b 1, 2 b 2 are mounted to the supporting member 2 a of the oscillator 2 and these magnets 2 b 1, 2 b 2 extend in width direction of the supporting member 2 a.

A plate-like ferrite magnet or rare earth magnet, etc. can be used as these magnets 2 b 1, 2 b 2, and the magnets 2 b 1, 2 b 2 are individually magnetized. The magnet 2 b 1, for example, presents north pole on the surface of its electromagnet 4 a side and south pole on the surface of its electromagnet 4 b side while the magnet 2 b 2 presents south pole on the surface of its electromagnet 4 a side and north pole on the surface of its electromagnet 4 b side. On application of AC current to the electromagnets 4 a, 4 b, either one of the electromagnets 4 a, 4 b has north pole at its center and south poles on both sides of it, while the other one has south pole at its center and north poles on its both sides, and these north pole and south pole change alternately in accordance with the change in the phase of an AC generator, such that the magnetic action of the magnets 2 b 1, 2 b 2 provided on the supporting member 2 a of the oscillator 2 causes attraction and repulsion forces between the magnets 2 b 1, 2 b 2 so as to allow the oscillator 2 to move in a reciprocating motion in axial direction. Accordingly, the diaphragm 3 vibrates so that the pump 1 suctions and discharges fluid repeatedly. These magnets 2 b 1, 2 b 2 also can be tightly fixed to the supporting member 2 a, for example by being integrally molded onto the resin of the supporting member 2 a during the formation of the supporting member 2 a by resin molding, etc.

A diaphragm 4 can be formed of ethylene propylene rubber (EPDM) or fluoro-rubber, etc. The center plates 6 a, 6 b can be formed of metal or plastic, etc. Because this diaphragm 4 is sandwiched at its center by the outer center plate 6 a and the inner center plate 6 b, the through hole 6 c communicates with from the outer center plate 6 a to the inner center plate 6 b through the diaphragm 3.

As shown in FIG. 1, the pump casing 5 is structured to be divided into a compression chamber 5A on the diaphragm 3 side, a suction chamber 5B and an exhaust chamber 5C by partition walls. A suction valve 5 a is provided between the compression chamber 5A and the suction chamber 5B such that when the volume of the compression chamber 5A increases to decrease a pressure, the suction valve 5 a opens to allow fluid to flow in from the suction chamber 5B, and when the volume of the compression chamber 5A decreases to increase pressure, the suction valve 5 a closes. While an exhaust valve 5 b is provided between the compression chamber 5A and the exhaust chamber 5C so that when the volume of the compression chamber 5A decreases to increase pressure, this exhaust valve 5 b opens to allow the fluid such as air in the compression chamber 5A to be discharged to the exhaust chamber 5C.

Next, a method of fixing the outer and inner center plates 6 a, 6 b sandwiching the diaphragm 3 at its center to the oscillator 2 will be described with reference to FIG. 3. First, a cylindrical projecting portion 6 b 1 is formed at the center of the inner center plate 6 b on its oscillator 2 side. While, at both ends of the supporting member 2 a of the oscillator 2, a circular concave groove 2 d terminated at the edges of side surfaces 2 a 2 (see FIG. 4) in thickness direction of the supporting member 2 a at the end is formed such that the above-mentioned projecting portion 6 b 1 fits around the mounting screw part 2 c.

Moreover, a cylindrical portion 2 e is formed because of this concave groove 2 d at the center of the end of the supporting member 2 a, and a ring-shaped groove 2 e 1 where a ring-shaped elastic member 7 can be inserted is formed on the outer periphery of the cylindrical portion 2 e. With an O-ring 7, as the ring-shaped elastic member, mounted to this ring groove 2 e 1, the mounting screw part 2 c is press fitted and embedded into the through hole 6 c extending through the center plates 6 a, 6 b and the diaphragm 4. Then, the top end of the mounting screw part 2 c projecting on the pump casing 5 side (right side of the drawing) is fastened through the washer 8 by the nut 9 so that the supporting member 2 a of the oscillator 2 and the diaphragm 3 can be fixed to each other.

Here, because the O-ring 7 is formed to have a larger diameter than that of the cylindrical portion 2 e, it is pressurized more strongly to contact with an inner wall surface 6 b 2 of the projecting portion 6 b 1 of the inner center plate 6 b, as well.

With such structure, when fluid (liquid or gas) suctioned into the compression chamber 5A is about to invade from the pump casing 5 side through the gap between the through hole 6 c formed on the diaphragm 3 and the outer and inner center plates 6 a, 6 b and the mounting screw part 2 c to the inside of the housing 10 having the oscillator 2 positioned therein, this invasion can be prevented by the O-ring 7. Therefore, the amount of fluid discharged from the compression chamber 5A is not less than the amount of fluid suctioned into the compression chamber 5A, and as a result, it is possible to prevent the decrease of the performance of the pump 1. Additionally, if the fluid is liquid, a failure of the pump 1 due to a short circuit caused by the invasion of the fluid to the oscillator 2 side can be prevented from taking place. Furthermore, because the pressure of the O-ring 7 is only in radial direction perpendicular to axial direction of the oscillator 2, it is not affected by how tightly the mounting screw part 2 c is fastened at a screw clamp part, and dimensional variation among members, etc. such as decentralization of oscillator 2 is not caused. Therefore, the performance of the pump 1 can be stabilized among products. Then, with the ring groove 2 e 1 formed beforehand on the outer periphery of the cylindrical portion 2 e of the supporting member 2 a of the oscillator 2, only by inserting the O-ring 7 into the ring groove 2 e 1 and press fitting it into the through hole 6 c of the inner center plate 6 b, the oscillator 2 and the diaphragm 3 can be assembled, and thus work efficiency during the assembly of the oscillator 2 and the diaphragm 3 is not worsened. Additionally, even when an unexpected external force is applied to the oscillator 2 during an assembling stage of the oscillator 2 and the diaphragm 3 and the like, the diaphragm is not damaged because of absorptive capacity of the O-ring 7 for such a large external force.

By the way, in this embodiment, as shown in FIG. 5, two U-shaped protruding portions 6 b 3, 6 b 4 are formed outside the cylindrical portion 6 b 1 on the inner center plate 6 b in a manner to sandwich the cylindrical portion 6 b 1, and the protruding portions 6 b 3, 6 b 4 are formed in a manner to entirely cover the outer peripheral side surface of the end of the supporting member 2 a. These protruding portions 6 b 3, 6 b 4 are structured to hold side surfaces excluding the cylindrical portion 2 e at both ends of the supporting member 2 a of the oscillator 2. Here, the “side surfaces” include a surface 2 a 1 in the thickness direction of the oscillator 2 and a surface 2 a 2 at the end of the planar part as shown in FIG. 4. Accordingly, even when the oscillator 2 is about to rotate with respect to the inner center plate 6 b, the side surface 2 a 2 of the supporting member 2 a of the oscillator 2 is stuck at the protruding portions 6 b 3, 6 b 4 of the inner center plate 6 b, and thus the oscillator 2 can be prevented from rotating. Thus, the pump 1 can be operated in a stable manner. Furthermore, the protruding portions 6 b 3, 6 b 4 serve as a guide when inserting the mounting screw part 2 c of the oscillator 2 into the through hole 6 c extending through the diaphragm 3 and the center plates 6 a, 6 b, so as to make the insertion work easy.

As shown in FIG. 1 and FIG. 6 which is an enlarged view of the portion A of FIG. 1, the diaphragm 3 has a flange 3 a formed on the outer peripheral edge and this flange 3 a is sandwiched by a diaphragm support 11 and the partition wall 5A1 of the compression chamber 5A of the pump casing 5 such that diaphragm 3 is fixed.

In this embodiment, as shown in FIG. 6, a circular rib 5A3 is provided, by integral molding, on the abutment surface 5A2 jointing the flange 3 a of the diaphragm 3 on the partition wall 5A1 of the compression chamber 5A, and this circular rib 5A3 digs into the abutment surface 3 a 1 jointing the partition wall 5A of the pump casing 5 at the flange 3 a of the diaphragm 3. Therefore, the sealing between the partition wall 5A1 of the compression chamber 5A of the pump casing 5 and the flange 3 a of the diaphragm 3 can be improved. As a result, the amount of fluid suctioned into the compression chamber 5A is prevented from decreasing to less than the amount of fluid discharged from the compression chamber 5A, and it is possible to prevent the decrease of the performance of the pump.

Additionally, if the circular rib 5A3 is provided on the partition wall 5A of the pump casing 5 as done in this embodiment, the circular rib 5A3 is not affected by the deformation of the diaphragm 3 during the operation of the pump 1, and thus the sealing as a rib is stabilized so that operation status of the pump 1 can be stabilized eventually.

EXPLANATION OF SYMBOLS

1 Electromagnetic vibrating diaphragm pump

2 Oscillator

2 a Supporting member

2 a 1, 2 a 2 Side surfaces

2 b 1, 2 b 2 Magnets

2 c Mounting screw part

2 d Concave groove

2 e Cylindrical portion

2 e 1 Ring-shaped groove

3 Diaphragm

3 a Flange

3 a 1 Abutment surface

4 a, 4 b Electromagnets

4 a 1, 4 b 1 Electromagnet cores

4 a 2, 4 b 2 Electromagnet coils

5 Pump casing

5A Compression chamber

5A1 Partition wall

5A2 Abutment surface

5A3 Circular rib

5B Suction chamber

5C Exhaust chamber

5 a Suction valve

5 b Exhaust valve

6 a Outer center plate

6 b Inner center plate

6 b 1 Projecting portion

6 b 2 Internal wall surface

6 b 3, 6 b 4 Protruding portions

6 c Through hole

7 O-ring

10 Housing

11 Diaphragm support 

What is claimed is:
 1. An electromagnetic vibrating diaphragm pump comprising: an oscillator having two magnets provided on at least one surface side of a plate-like supporting member made of non-magnetic material and having mounting screw parts fixed to both ends of a central axis of the supporting member; disc-shaped diaphragms fixed to the mounting screw parts at both ends of the supporting member; an electromagnet provided to face the magnets; and pump casings fixed to respective outer peripheries of the diaphragms provided at the both ends and individually covering the outer side of the diaphragms, wherein the diaphragm is sandwiched by an inner center plate provided on the magnet side of the diaphragm and an outer center plate provided on the side opposite to the magnet side of the diaphragm, the end of the oscillator is inserted into and fixed to a through hole provided at the center of the inner and outer center plates, and a cylindrical projecting portion is formed at the center of the inner center plate on the oscillator side, a concave groove capable of fitting the projecting portion is formed at the end of the supporting member of the oscillator and a ring-shaped elastic member is placed between the outer periphery of a cylindrical portion formed when the concave groove is formed and the inner periphery of the cylindrical projecting portion, such that leakage from a gap portion between the through hole of the inner and outer center plates and the end of the oscillator is prevented in an air-tight manner.
 2. The electromagnetic vibrating diaphragm pump according to claim 1, wherein a protruding portion for holding the side surfaces of both ends of the supporting member constituting the oscillator is formed on the surface of the inner center plate on its oscillator side so as to position the supporting member.
 3. The electromagnetic vibrating diaphragm pump according to claim 2, wherein the protruding portions are formed in a manner to entirely cover the outer peripheral side surface of the end of the supporting member.
 4. The electromagnetic vibrating diaphragm pump according to claim 1, wherein the concave groove is a circular concave groove terminated at the edges of side surfaces in thickness direction of the supporting member at the end.
 5. The electromagnetic vibrating diaphragm pump according to claim 1, wherein the pump casing has a compression chamber adjacent to the diaphragm, an exhaust chamber connected to the compression chamber via an exhaust valve and a suction chamber connected to the compression chamber via a suction valve, and a rib digging into the diaphragm is formed on a joint surface jointing the diaphragm on a partition wall of the compression chamber.
 6. The electromagnetic vibrating diaphragm pump according to claim 5, wherein the rib is formed to be circular and digs into a flange part formed at the end of the diaphragm in a circular manner so that the partition wall and the diaphragm are jointed.
 7. The electromagnetic vibrating diaphragm pump according to claim 6, wherein the mounting screw part is integrally fixed to the supporting member made of resin during the formation of the supporting member by resin molding.
 8. The electromagnetic vibrating diaphragm pump according to claim 1, wherein the diaphragm is formed of ethylene propylene rubber (EPDM) or fluoro-rubber compact.
 9. The electromagnetic vibrating diaphragm pump according to claim 1, wherein the magnets are permanent magnets made of a plate-like ferrite magnet or rare earth magnet.
 10. The electromagnetic vibrating diaphragm pump according to claim 9, wherein the magnets are integrally fixed to the supporting member made of resin during the formation of the supporting member by resin molding. 